Question

I’m running into a problem with the following Python 3.2.2 code. The code is an attempt to do some timing tests of another application I’m testing. The idea is to have another script (of any variety) get passed into the timer program and make some changes to the environment. That script should run in a separate thread, so that I can start timing from the start of the script instead of the end. The rest of this script times the application’s reaction to that script. I’ve attempted to draw from the threading module documentation to create this, and I’m confident that I’ve read it thoroughly, but I’m consistently running into the following error using this code:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python32\lib\threading.py", line 669, in start
    if not self._initialized:
AttributeError: 'str' object has no attribute '_initialized'

Here’s the thread class definition.

import threading, ...

class AsyncScript(threading.Thread):
    def __init__(self, s):
        self.script = s
    def run(self):
        print ("Beginning script...")
        try:
            os.system("cmd /k " + self.script)
        except:
            sys.exit("Error running script " + self.script)

This is called elsewhere in the script by AsyncScript.start(options.script), where the options class contains the options passed into the script (using the argparse module.)

Any ideas about what I might be doing wrong here?

---

Okay, an update. The following (stripped-down) version of the code DOES work, and I’m honestly not sure why — I don’t see the difference.

import threading

class AsyncScript(threading.Thread):
    def __init__(self, s):
        threading.Thread.__init__(self)
        self.script = s
    def run(self):
        print("This would run script " + self.script)

AsyncScript("sample script path string").start()

Output is, appropriately,

This would run script sample script path string

Aside from the inclusion of threading.Thread.__init__(self), which I had previously included in earlier versions of this code without success, I’m not really sure what’s different here. What am I missing?

Answer 1

You don’t need to use threads if you run the script in a separate process anyway. Use subprocess instead of os.system().

You don’t need to subclass Thread to create a thread:

Thread(target=func, args=func_args).start()

I’m not really sure what’s different here. What am I missing?

There are two differences:

1. AsyncScript.start(options.script) vs. AsyncScript(options.script).start().

   AsyncScript is a class object. AsyncScript(options.script) is an instance of that class.

   AsyncScript.start(options.script) calls an unbound .start method. It expects its first argument to be an AsyncScript instance not a string options.script. The correct way to call a method is obj.method(). In your case obj = AsyncScript(options.script).

2. Presense of threading.Thread.__init__(self) in the AsyncScript.__init__() method.

   If you don’t call threading.Thread.__init__(self) then Thread’s attributes such as _initialized are not created/defined.